US 10001400

I'll search for this specific patent number and any related litigation.

US Patent 10,001,400 — Summary

Important caveat on scope of search: I ran targeted searches for this exact number (US 10,001,400 / US10001400) against publicly indexed sources. I found the patent's own record and family/publication data, but no CAFC 2026 docket, district-court litigation, or PTAB proceeding naming this patent surfaced. I do not have authoritative access to live PACER/CAFC docket systems through these tools, and absence of results in a web index is not proof that no such proceeding exists. Treat the "no litigation found" statement as a search limitation, not a legal conclusion. All bibliographic and claim data below come from the patent text itself.

Bibliographic data (per the authoritative patent record)

Family members (same priority): JP 6372180 B2, KR 101849024 B1, BR 112016000640 B1, WO 2015/008457 A1.

Abstract (verbatim)

A liquid-level detection device includes a rotatable body that rotates in accordance with a liquid surface, a fixation body that includes a main body part fixed to a container and a supporting part projecting from the main body part in an axial direction along a rotation axis of the rotatable body to rotatably support the rotatable body, a pair of magnet parts that are held by the rotatable body in an arrangement positioning the supporting part therebetween and that generates a magnetic flux passing through the supporting part, and a detecting part that includes a magnetoelectric conversion device disposed in the supporting part and that outputs a detection result according to a density of the magnetic flux passing through the magnetoelectric conversion device. The rotatable body includes a magnetic shield member entirely covering a projection region of a space located between the pair of magnet parts, which is projected outward in the axial direction, to limit leakage of the magnetic flux. The magnetic shield member is located outward of the supporting part and the pair of magnet parts in the axial direction to include an exposed surface which is exposed into the container.

Independent claim overview

This patent has one independent claim — claim 1. Claims 2–8 all depend, directly or indirectly, on claim 1 (2→1; 3→1; 4→3; 5→1; 6→1; 7→1; 8→7).

Claim 1 (independent) — plain language:
A fuel/liquid-level sensor built around a Hall-effect scheme. It requires:

• a rotatable body (the "magnet holder") that turns as the liquid surface moves;
• a fixation body with (a) a main body fixed to the container and (b) a supporting part (shaft) projecting axially that rotatably supports the rotatable body;
• a pair of magnet parts carried by the rotatable body, straddling the supporting part and driving magnetic flux through that supporting part;
• a detecting part with a magnetoelectric conversion device (Hall IC) located inside the supporting part, outputting a signal based on flux density through it.
• The two characterizing limitations: (i) the rotatable body includes a magnetic shield member that entirely covers the "projection region" — i.e., the footprint of the space between the two magnets, projected outward along the axis — to limit flux leakage; and (ii) that shield member sits axially outboard of both the supporting part and the magnet pair and presents an exposed surface exposed into the container (the liquid).

The point of the invention (from the specification): In the cited prior art (JP 2006-153679 A / Nippon Seiki), metallic debris in the fuel could still perturb the field even without touching the magnet, because leakage flux escaped past the exposed face. By covering the entire projection region with a shield, the leakage is confined so that any metallic debris collecting on the exposed surface forms a predictable magnetic circuit rather than randomly distorting the field through the Hall element, stabilizing the sensor output.

Dependent claims (for context, not independent):

• Claim 2: flux density through the shield from each magnet does not exceed the shield's saturation flux density.
• Claim 3: the shield is a bottomed cylinder containing the magnet pair.
• Claim 4: adds that the magnetoelectric conversion device is placed axially outboard of the shield's end surface (the third embodiment, external-field protection).
• Claim 5: shield is made of magnetic powder mixed with resin.
• Claim 6: the entire rotatable body is formed as the magnetic shield member.
• Claim 7: shield = main body plate part + integrally formed cylindrical plate part; exposed surface on the plate; cylindrical plate fitted on the magnets' outer peripheral surface.
• Claim 8: the cylindrical plate part is fitted between the magnets' outer surface and the rotatable body.

Uncertainty notes

• No CAFC 2026 or district-court docket activity for US 10,001,400 was found in my searches. I cannot confirm from an authoritative docket source that none exists; my tools do not give me live PACER/CAFC docket access, so this should not be read as a definitive negative.
• Bibliographic fields above are stated literally as they appear in the patent record (including the priority/filing distinctions between the July 16, 2013 JP priority and the July 9, 2014 PCT/US filing date).
• The patent text is the authoritative source here; search results did not conflict with it.

I'll search litigation-tracking sources for this specific patent number.

Initial results found no litigation on this patent number. Let me run additional targeted queries on litigation aggregators.

Litigation Search Results for US Patent No. 10,001,400

Bottom line: No litigation involving US Patent No. 10,001,400 was found.

What I searched and what I found

Case-by-case table

Important limitations on this answer

1. "No litigation found" ≠ "no litigation exists." The searches I could run returned no indexed record of any district-court complaint, CAFC appeal, ITC § 337 investigation, or PTAB proceeding naming this patent. A negative in a web index is a search limitation, not a legal conclusion.
2. I do not have direct, live access to authoritative docket systems. The task points to Unified Patents' litigation caselist, PACER, and CAFC dockets; my available tools cannot query those systems directly, and my remaining queries (including the Unified Patents and PTAB-specific searches) were cut off by a tool-step limit before returning data. A definitive clearance check would require running this patent number directly against PACER's docket search, the CAFC docket, the ITC EDIS system, and the PTAB API/PTAITS.
3. Note this is consistent with the earlier analysis in the previously generated summary, which also found no litigation or PTAB activity for this patent. Nothing in the present search contradicts that finding.

Context that may explain the absence of litigation

US 10,001,400 is a component-level fuel-level sensor patent owned by DENSO Corporation — an operating automotive supplier, not an NPE/assertion entity. Patents of this type are frequently practiced internally by the owner and its supply chain rather than litigated. Notably, the family/publication record lists the same priority family across JP 6372180 B2, KR 101849024 B1, BR 112016000640 B1, and WO 2015/008457 A1; and closely related Denso liquid-level patents appear in the "similar documents" set (e.g., US 9,677,926 B2, US 9,857,213 B2). Any enforcement activity would more plausibly appear against the later-issued relatives, but that is outside the specific-number search you asked for and I did not confirm it.

Recommendation for a definitive answer

To confirm the negative authoritatively, run the literal number 10001400 (and separately US 10,001,400) against:

• PACER Case Locator (search "Patent" nature of suit),
• CAFC docket search by patent number,
• USITC EDIS for § 337 complaints,
• PTAB API / PTAITS for IPR/PGR/CBM petitions,
• Unified Patents Litigation caselist and Docket Navigator (subscription).

PTAB / AIA Trial Analysis — US 10,001,400 B2

Source of the proceedings list: the structured "PTAB proceedings on file" block in this prompt (USPTO Open Data Portal). I also ran corroborating web searches against PTAB/PTACTS-indexed documents, Federal Circuit and CourtListener-type sources, and general web indexes for the patent number, the patent title, the assignee, and the inventor.

Proceedings overview

There are zero AIA trial proceedings on file for US 10,001,400 — no IPR, no PGR, and no CBM — so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials, and the defensive posture for a defendant is that all eight claims (1–8) are wholly untested and fully intact: the patent has never been subjected to a PTAB validity challenge, meaning there is no cancelation to leverage and no § 315(e)(2) estoppel to preserve.

Critical caveat on negative findings. The absence of proceedings below reflects (a) the canonical structured data returned for this patent and (b) my searches. I do not have live PACER/CAFC or PTAB E2E docket credentials through these tools, and a proceeding on a recently-filed petition may simply not be indexed yet. Treat "none found" as a well-supported search result, not a certified negative. Verify independently at PTAB E2E / PTACTS and CourtListener before relying on it in a brief.

Contamination warning — do not conflate these " '400" patents

My searches repeatedly surfaced unrelated patents also called "the '400 patent." None of the following involves US 10,001,400, and a PTAB record for any of them must not be attributed to Denso's liquid-level patent:

None of these share a patent number, title, assignee, or technology with US 10,001,400. If you see an "IPR on the '400 patent" cited against a fuel-level sensor, it is a mis-citation.

Proceedings

None. There is no proceeding number to report, and I will not invent one.

For completeness, the AIA-proceeding-specific fields you asked for resolve as follows:

• Type: n/a
• Filed: n/a
• Status: n/a — the structured data reports no AIA trial proceedings
• Judge panel: n/a
• Petition grounds: n/a
• Institution decision: n/a
• Final Written Decision: n/a — no FWD exists, so no claim has been canceled, and no claim has been affirmed by the Board either
• Settlement / termination: n/a
• Appeal: no PTAB FWD exists to appeal, so there is no CAFC docket arising from an AIA trial
• Defensive value: Because nothing has been invalidated, a defendant cannot point to a cancelation order. Every claim the patent owner asserts — including independent claim 1 and its seven dependents — reaches the merits untested.

Strategic summary

Claim status: 1–8 all UNTESTED (all presumed valid and enforceable). There is no IPR certificate, no statutory disclaimer on the public record for this patent, and no PTAB-sustained subset to point at. Contrast this with the near-neighbor Denso liquid-level family member that did draw attention: the Google Patents record for US 10,001,400 lists US 9,857,213 B2 ("Liquid-level detection device") and US 9,677,926 B2 among similar documents, and the patent's own citation list shows a dense Denso/Nippon Seiki/Yazaki prior-art cluster (e.g., JP 2004-333283 A; JP 2005-010047 A / US 2005/0083045 A1 (Miyagawa); JP 2006-153679 A (the Patent Document 1 that this patent distinguishes); US 7,331,225 B2; US 2012/0121931 A1). None of that art has been run through an AIA trial against this patent.

Estoppel landscape: empty. Because no petitioner has ever filed an IPR/PGR on this patent, § 315(e)(2) and § 325(e)(2) estoppel do not attach to anyone. That cuts both ways:

• Favorable: For a defendant being asserted against today, the entire prior-art field remains available — including art that is "the same or substantially the same" as what the examiner considered, art from the patent's own cited references, and the JP-language family documents (JP 6372180 B2 is the JP counterpart; JP 2015-038470 A is the JP publication). You are not boxed out of any § 102/§ 103 ground by someone else's earlier petition.
• Unfavorable: You also get no free ride. There is no prior petitioner's work product, no institution decision to build on, and no FWD reasoning to adopt.

Pattern signals. No petitioner has filed even once on this patent, so there is no serial-petitioner pattern, no General Plastic / follow-on attack issue, and no defensive aggregator (Unified Patents or similar) in the chain. The patent owner (DENSO Corporation) shows no history of PTAB appellate litigation on this patent, because there is no PTAB decision to appeal. The only third-party disputes involving Denso and "fuel senders" that surfaced in my searches are antitrust price-fixing class actions (the automotive-parts cartel litigation) — not patent validity challenges, and not directed at US 10,001,400. Administrative note: the record shows a maintenance-fee reminder mailed 2026-02-09 and an earlier 4th-year fee paid 2021-12-08, with adjusted expiration listed as 2034-11-23 — i.e., the patent remains in force, so the next live question is whether the fee is paid, not whether the claims survive.

Recommended next steps

If you are a defendant and the patent owner is asserting US 10,001,400:

1. There is no FWD to quote. Do not represent to a court or an adversary that any claim of this patent has been canceled or held unpatentable. It has not. The complete claim set 1–8 stands.

2. The absence of any IPR is itself a signal — but read it carefully. Well-asserted, high-value patents usually attract at least one IPR within a few years of assertion. Zero petitions here most likely means the patent has not been widely asserted (consistent with the earlier section's finding that no district-court or CAFC litigation naming it was located), rather than that it is unassailable. This is a claim-construction and invalidity-defense procedural question, not a "the troll has no case" situation — the opposite: the plaintiff has a clean, never-narrowed claim set.

3. If you have been served with a complaint asserting this patent, the § 315(b) one-year clock is the gate. You may file an IPR within one year of service of the complaint. Given that claim 1's distinguishing limitations are the "projection region ... entirely covered" shield and the "exposed surface ... exposed into the container" requirement, the productive IPR grounds are § 103 combinations built on JP 2006-153679 A (Nippon Seiki) — the very reference the patent criticizes — optionally in view of JP 2004-333283 A or US 2005/0083045 A1, plus a printed-publication teaching of covering the inter-magnet volume to contain leakage flux. Enablement/written-description attacks under § 112 on the "does not exceed a saturated magnetic flux density" limitation of claim 2, and on the structural relationship in claims 7–8, are secondary options.

4. Statutory timeline to plan around, if a petition is filed: PTAB must decide institution within ~6 months of the petition's filing-date-accorded notice; the patent owner's preliminary response is due within 3 months of that notice; and any Final Written Decision is due within 1 year of institution (35 U.S.C. § 316(a)(11)). Cite the opinion you rely on via PTAB E2E/PTACTS and, for any eventual CAFC disposition, CourtListener.

5. Before committing to any of the above, independently confirm the negative. Search PTAB E2E/PTACTS by patent number (10,001,400), by application number (14/904,341), and by the family members (JP 6372180 B2, KR 101849024 B1, BR 112016000640 B1), and check the CAFC docket and CourtListener for appeals. My tools cannot see unindexed or very recent filings, and this is the one conclusion a defendant must not adopt on faith.

I'll research the assignment record for this patent, starting with the USPTO Assignment Center data and cross-referencing.

Research limitation (read first)

I do not have live, authenticated access to USPTO Assignment Center (assignmentcenter.uspto.gov) or the Assignment API through my tools; my searches returned the patent's own record and family data but no independently retrievable assignment-search page for US 10,001,400. The single recorded assignment below is drawn from the authoritative patent record's own legal-events table, which reproduces the Assignment Center entry verbatim (conveyance type, assignor, assignee, execution date, recording date, and reel/frame). One field the source record does not expose is the correspondent (recording attorney/firm of record). I flag that gap explicitly rather than guess. All "no further records" statements are search limitations, not definitive legal negatives.

Inventors

Pattern check: One inventor, one employer, no co-inventors and no third-party assignees. There is no evidence of inventor departure or an inventor-side transfer — the assignment runs to the employer, not away from it. The inventor's name also appears on the citation list as the inventor of US 2005/0083045 A1 (a Denso liquid-level detector), consistent with a long-tenured Denso engineer rather than a departing founder. No fire-sale precursor signal.

Original assignee

DENSO Corporation (DENSO Corp / DENSO CORPORATION, Kariya, Aichi, Japan).

• Business: Tier-1 automotive supplier (thermal, powertrain, electrification, sensors). Fuel-pump modules and in-tank level sensors are a core product line; the specification itself describes the device as "held by a fuel pump module 93" inside a fuel tank 90 — i.e., Denso ships the commercial embodiment (OEM fuel sender units).
• Public status: Publicly traded operating company (Tokyo Stock Exchange, ticker 6902); no bankruptcy, no assignment-triggering reorganization in this chain.
• Ownership status today: Still the assignee of record. The patent is listed Active, with adjusted expiration 2034-11-23; the 4th-year maintenance fee was paid 2021-12-08 and an 8th-year reminder was mailed 2026-02-09.

Assignment timeline

Exactly one recorded assignment exists for US 10,001,400.

• 2015-12-08 (executed) / recorded 2016-01-11 — Reel 037455/0307
  • Conveyance: Assignment — "ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS)"
  • Assignor: MIYAGAWA, ISAO
  • Assignee: DENSO CORPORATION
  • Correspondent: Not exposed in the source record I retrieved. The Google Patents legal-events entry for the 2016-01-11 recording does not reproduce the correspondent name/firm. I cannot state it without fabricating it. (In Denso's typical practice, Japanese-origin national-phase records of this vintage are signed by a corporate IP-department attorney of record; I am not asserting a name.)
  • Context: Routine inventor-to-employer assignment — the employment/priority-rights assignment executed in connection with the 35 U.S.C. § 371 national-phase entry of PCT/JP2014/003647 (effective date stated as 2015-12-08, recorded 2016-01-11, ~5 weeks after the US national-phase filing date of 2014-07-09 and ~2.5 years before issuance).

Post-issuance: No subsequent assignments of any kind appear — no further Assignment, Security Agreement, Merger, Change of Name, License, Release, or Correction entry between issuance (2018-06-19) and today. No security interest / collateral lien was ever recorded against this patent.

Timeline diagram

timeline
    title Ownership of US 10001400
    2013 : JP priority application filed
    2014 : PCT and US national phase filed
         : Denso is original applicant
    2015 : Inventor Miyagawa assigns rights to Denso
    2016 : Assignment recorded at USPTO
    2018 : Patent issued to Denso Corporation
         : No further assignments recorded
    2034 : Scheduled adjusted expiration

NPE / troll-pattern signals

Net count: 0 signals present, 1 signal undeterminable (correspondent field not retrievable).

Verdict

Insufficient data — applied strictly, because the record contains only the original inventor-to-employer assignment (reel 037455/0307, executed 2015-12-08, recorded 2016-01-11), and the framework reserves "operating-company assertion" for cases where the holder is provably suing competitors and "defensive/non-asserting" for chains that terminate at a defensive aggregator (RPX/AST/LOT/Unified/OIN) — neither of which is established here.

Substantively, however, this is the benign end of the spectrum: US 10,001,400 has never left DENSO Corporation, a listed operating manufacturer that ships fuel-level sender units embodying the claims, and shows zero post-issuance transfers, zero security interests, zero shell-entity names, and zero NPE-list assignees across its entire 2018–2026 ownership history. There is no NPE or troll-pattern signal to report; the only unresolved item is the unretrievable correspondent field on the single 2016 recording.

Verify directly: USPTO Assignment Center — search patent number 10001400 (https://assignmentcenter.uspto.gov/), cross-checked against the patent's legal-events table at https://patents.google.com/patent/US10001400/en (Reel/Frame 037455/0307) and USPTO Patent Center for application 14/904,341.

I'll research this systematically. Let me start with targeted searches.

Let me gather details on the key cited references.

Prior-Art Analysis — US 10,001,400 B2 (App. 14/904,341)

1. Target patent — confirmed

My search returned the exact record requested: US 10,001,400 B2, "Liquid-level detection device," DENSO Corp., inventor Isao Miyagawa, app. 14/904,341, §371 national phase of PCT/JP2014/003647, earliest priority 2013-07-16 (JP 2013-147712), issued 2018-06-19. This is the same document supplied and confirmed as authoritative in the earlier section, so I will not repeat its bibliographic fields.

Applicable §102 regime (new in this section): Because the effective filing date (2013-07-16 priority / 2014-07-09 PCT-US filing) is after 2013-03-16, the AIA first-inventor-to-file provisions apply. Therefore:

• §102(a)(1) art = printed publications/patents public before the effective filing date;
• §102(a)(2) art = U.S. patents and U.S. application publications effectively filed before that date (even if published later).

Methodology caveat (important): I worked from the authoritative patent text and the citation metadata for the 21 references the Office cited against US 10,001,400 (plus the one "family-cites-family" reference). I retrieved full abstract/description text for several references but not for all of them. Where I did not obtain a reference's full disclosure, I say so and characterize the §102 conclusion as apparent/preliminary rather than final. Anticipation under §102 requires a single reference to disclose every limitation as arranged; I flag below where a reference is really §103 (obviousness) material.

2. Examiner-cited references

The examiner-cited group (no "†" in the record) is: JPH1123213A, JP2001264006A, JP2003214896A, JP2004333283A, JP2005010047A†, US20050083045A1†, US20080072668A1†, JP2006153679A, US7331225B2†, US20070090832A1†, US20080231267A1†, JP2008224574A, US20120011931A1†, US20120174667A1†, US20120210782A1†, US20120285240A1†, US20120304761A1†, WO2013099544A1, US20160123789A1†, US20160161321A1†, plus JP2013137256A.

Family-cites-family reference:

Priority document (not prior art): JP 2014-123434 / JP 6372180 B2 is the applicant's own priority application and JP family member (same invention). It cannot be §102 art against US 10,001,400.

3. Bottom line on §102

No single cited reference appears to anticipate any of claims 1–8 of US 10,001,400. Every reference that touches the architecture is missing at least one limitation of independent claim 1, and the two limitations that drive the claim are the hardest to find in a single reference taken alone:

1. "a pair of magnet parts … in an arrangement positioning the supporting part therebetween" — found in US20080231267A1 (pair of magnets 6 + Hall element 7) and in US20160161321A1, but in each case without the shield limitation; and
2. "magnetic shield member entirely covering a projection region of a space located between the pair of magnet parts … [with] an exposed surface which is exposed into the container" — the shield aspect appears in JP2006153679A (Nippon Seiki, iron-nickel cup shield on a ring magnet) and WO2013099544A1 / JP2013137256A (Nippon Seiki shield case), but in each case the shield is paired with a single cylindrical/ring magnet and is not shown to cover the claimed "projection region between the pair of magnet parts."

The references are therefore best characterized as §103 (obviousness) art, not §102 anticipation art.

Closest art, ranked

1. JP2006153679A (Nippon Seiki) — the patent's own "Patent Document 1"; shield-cup-over-magnet, detection element in the bearing/shaft. Primary §103 reference; most pertinent to claim 3 (bottomed-cup shield) and to the general shield concept.
2. WO2013099544A1 / JP2013137256A (Nippon Seiki) — shield case + Hall at the rotation center; predates the priority date.
3. US20080231267A1 (Denso) — pair of magnets with the Hall element in the shaft bearing; supplies the missing "pair of magnet parts … supporting part therebetween" element that JP2006153679A lacks.
4. US20050083045A1 / JP2005010047A (Denso/Miyagawa) and US20070090832A1 (Denso) — baseline non-contact liquid-level architecture (rotatable body, shaft, Hall IC, magnet).
5. US20160161321A1 (Denso) and US20160123789A1 (Multidimension) — potential §102(a)(2) art on the paired-magnet + Hall-in-shaft architecture, still lacking the claimed shield/exposed-surface feature.

Two specific flags

• Inventor overlap: US20050083045A1 and US20080072668A1 (US 7,458,261 B2) name Isao Miyagawa, the same inventor as US 10,001,400. That does not by itself remove them as art, but it signals they are Denso's own earlier work and are likely cited as showing the state of the applicant's own technology.
• Possible uncited art: The patent's "Similar Documents" list includes US 9,453,756 B2 (the Nippon Seiki shield-case family, i.e., the WO2013099544A1 counterpart), US 9,677,926 B2, US 9,857,213 B2, and US 9,810,570 B2 (Nippon Seiki). I did not verify whether any of these were substantively applied; if they were not examiner-cited, they are candidates for additional prior art worth checking, particularly US 9,453,756 B2.

Search limitation (repeated from the prior section, still applicable): I do not have authoritative live USPTO PatentCenter/PACER access through these tools, so the above is drawn from the patent text and indexed citation metadata. Reference descriptions for entries I did not open in full (#1, #2, #3, #9, #12–#17, #20, and EP1628115A1) are characterized at a preliminary level; confirm their full disclosures before relying on any §102 conclusion.

I'll research the key prior-art references cited on this patent's page to ground the obviousness analysis.

I have strong content on the primary reference and several key secondary references. Let me gather details on a few more references cited on the page.

Obviousness Analysis — US 10,001,400 B2 under 35 U.S.C. § 103

Scope note. This analysis uses the twenty prior-art references listed in the "Citations" section of the US10001400 Google Patents page (https://patents.google.com/patent/US10001400/en), plus the patent's own specification. I treat the patent text as authoritative. Where I describe a reference's disclosure, I cite the passage/URL I actually retrieved. This is a technical/patent-analyst exercise, not legal advice; the reference list on the patent page reflects references of record, not a litigation record.

1. Framework

Under § 103 and KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), a claim is obvious when the differences between the claimed subject matter and the prior art are such that the subject matter as a whole would have been obvious to a person having ordinary skill in the art (POSITA) at the effective filing date (here, the 2013‑07‑16 JP priority / 2014‑07‑09 PCT filing). I apply the Graham v. John Deere factors: (1) scope/content of the prior art; (2) differences from the claims; (3) PHOSITA level; (4) secondary considerations.

Caution on outcome. The examiner cited many of these references and still allowed the claims (see the "cited by examiner" asterisks and the grant at 2018‑06‑19). A § 103 attack therefore has to do more than recite the references — it must supply an articulated motivation and reasonable expectation of success for the specific combination. I flag below where that motivation is strong versus where it is strained.

2. Person Having Ordinary Skill in the Art

A POSITA here is a mechanical/electro-mechanical engineer with ~2–4 years' experience designing non‑contact (magnet + magnetoelectric‑conversion‑element) automotive fuel‑level sensors, familiar with: float/arm/magnet‑holder kinematics; Hall‑IC signal conditioning; and magnetic shielding (iron‑nickel shield cans, flux‑path shaping, saturation behavior). This is a mature, crowded art — a strong KSR signal favoring combination.

3. The Claims

Claim 1 is the sole independent claim; claims 2–8 depend from it (2→1; 3→1; 4→3; 5→1; 6→1; 7→1; 8→7). The two characterizing limitations relative to admitted art are: (i) the rotatable body includes a magnetic shield member entirely covering the "projection region" — the footprint of the inter‑magnet space projected outward along the rotation axis — to limit flux leakage; and (ii) that shield sits axially outboard of the supporting part and the magnet pair and presents an exposed surface exposed into the container (the fuel). The specification frames the problem as metallic debris in the fuel collecting on that exposed surface and, absent full coverage, forming an unpredictable leakage‑flux circuit that corrupts Hall output (see the "SUMMARY" and background discussion in the patent).

4. The Prior-Art Landscape (from the page's Citation list)

A. JP 2006‑153679 A — Nippon Seiki ("Liquid level detector") — the patent's own "Patent Document 1." Retrieved text (https://patentimages.storage.googleapis.com/f2/5e/52/cb010b49cd26cd/JP2006153679A.pdf) shows claim 1: a bearing member on a main‑body frame, a holder rotatably supported on the bearing, a float arm, a ring magnet at the outer periphery of the bearing, a detection element in a part of the bearing member, and a magnetic shield member arranged to surround the ring magnet. Claim 4 recites the shield being cup‑shaped and covering the bottom and outer peripheral surface of the magnet. This is the closest single reference and discloses most of claim 1's architecture — rotatable body, fixation body with shaft/bearing, magnet held about the shaft, element inside the shaft, and a cup shield over the magnet's bottom/outer periphery. The patent concedes this.

B. US 7,331,225 B2 — Yazaki ("Non-contact type liquid level sensor"). Retrieved content (https://patents.google.com/patent/US7331225) discloses an electromagnetic shield plate mounted on the housing, disposed so as to cover the stators and the magnetoelectric converting element, made of sheet iron (ferromagnetic metal), positioned on the housing outer surface outboard of the detection side, with a part parallel to the inspection surface of the element. It expressly teaches that the shield plate "prevents the magnetoelectric converting element from being affected by an external magnetic field" and that its shape should avoid disturbing the magnet's own field (notched portion facing the magnet/rotational shaft).

C. US 2005/0083045 A1 — Miyagawa (Denso) and US 7,458,261 / US 2008/0072668 A1 (Denso). These disclose the baseline non‑contact architecture: magnet holder with hole, a main body with a shaft portion pivotally holding the holder, a float arm, and a magnetoelectric conversion element fixed to the main body so as to cross the magnet's flux (retrieved at https://patents.google.com/patent/US20050083045 and https://patentimages.storage.googleapis.com/3f/8e/49/a2b28546de0bec/[US8028575](/patent/US8028575).pdf).

D. US 2007/0090832 A1 — Denso ("Liquid level detecting device…"). Discloses a hollow shaft rotatably supporting the rotary member and accommodating the detection element/case inside the hollow shaft, with a Hall IC and chip components (retrieved at https://www.freepatentsonline.com/[7703322](/patent/7703322).html). Directly supports placing the magnetoelectric conversion device in the supporting part.

E. US 2012/0011931 A1 — Ichisawa (Nippon Seiki). Discloses a shield case formed of iron‑nickel, cup‑shaped (cylindrical portion + bottom portion), formed so as to surround the magnet, the detection element, and the circuit board, and covered by the case body (retrieved at https://patents.google.com/patent/US20120011931A1/en and the corresponding WO 2010/110028).

F. US 2015/0000398 A1 / US 9,453,756 B2 — Nippon Seiki (WO 2013/099544 A1, "Liquid surface detecting apparatus"). Same family as a reference of record; discloses a holder with a cylinder section containing the magnet, and a shield case of iron‑nickel with a cylinder section + flange provided "so as to cover the cylinder section of the holder" — i.e., a shield wrapping the magnet region (retrieved at https://patents.google.com/patent/US20150000398 and https://patents.google.com/patent/US9453756).

G. Other cited art further fills gaps: US 7,331,225 (shield placement), US 2016/0161321 A1 (Denso "Liquid surface sensing device," sibling, priority 2013‑07‑01), US 2016/0123789 A1 (Multidimension "Liquid level sensor system"), Gems Sensors US 2012/0210782 A1, the rotation/angle‑sensor art (JP H11‑23213, JP 2001‑264006, JP 2003‑214896, JP 2008‑224574), and EP 1 628 115 A1 (Key Safety Systems "Magnetic sensor system").

5. Primary Combination A — Claim 1

JP 2006‑153679 A in view of US 7,331,225 B2.

JP '679 supplies every pre‑characterizing element of claim 1 and a cup shield over the magnet's bottom/outer periphery. The differences are the two characterizing limitations: (i) the shield wholly covers the projection region of the inter‑magnet space; and (ii) the shield is axially outboard with an exposed container‑facing surface.

Yazaki '225 supplies both: an electromagnetic shield plate that is expressly laid outboard of the detection side and dimensioned to cover the stators and the magnetoelectric converting element, with a portion parallel to the element's inspection surface — i.e., a flat shield wall spanning the entire detection footprint, exactly the geometry of "entirely covering the projection region … projected outward in the axial direction." Yazaki's shield is thus a top/side plate positioned beyond the magnet/element along the axis, presenting an outwardly facing surface.

Motivation to combine. Both references are analogous art (vehicle fuel‑tank, float/magnet, Hall‑based level sensors), addressing the same problem — stabilizing the magnetoelectric output. JP '679's stated secondary objective is suppressing adverse effects of foreign matter in the liquid; Yazaki's is shielding the detection region from stray fields while not disturbing the magnet's field. A POSITA seeking to harden JP '679's sensor would look to Yazaki for a shield that, rather than only wrapping the magnet's bottom/periphery, spans the whole element‑facing footprint, and would place it outboard with the holder cover — a predictable, mechanical substitution of a known shield geometry with an expected benefit (confining leakage flux so debris on the exposed face forms a bounded, non‑corrupting circuit). KSR endorses precisely this: combining known elements, each performing its known function, for an expected improvement.

6. Alternative/Supplementary Combinations

• JP '679 + US 2007/0090832 (Denso) or US 2005/0083045 (Miyagawa) supplies the "detecting part … disposed in the supporting part" (hollow shaft accommodating the element) and the pair‑of‑magnets‑straddling‑the‑shaft architecture. These are the same assignee/family line as the patent and read as near‑admissions of the base architecture.
• JP '679 + US 2012/0011931 (Ichisawa) or US 9,453,756 (Ogasawara/Nippon Seiki) supplies a cup‑shaped shield that surrounds magnet + element and covers the magnet's cylinder — reinforcing full coverage of the projection region and the "bottomed cylinder" geometry of claim 3 and the plate+cylinder geometry of claims 7–8.

7. Dependent Claims

• Claim 2 (flux density through shield ≤ shield saturation): a result‑effective design parameter whose satisfaction is a matter of routine sizing (thickness/material of the shield). Yazaki's express concern that the shield not perturb the magnet's field cues the POSITA to operate the shield below saturation. Obvious as an optimization.
• Claim 3 (bottomed‑cylinder shield containing the magnets): taught squarely by JP '679 claim 4 (cup shape) and Ichisawa's cylindrical portion + bottom portion.
• Claim 4 (element outboard of the shield's end surface): the third‑embodiment geometry; placing the element outside the shield end (so the shield blocks external fields but the element still senses the magnet) is suggested by Yazaki's outboard, element‑covering plate and by the family's own disclosures; obvious as placement optimization.
• Claim 5 (shield from magnetic powder + resin): the patent's own first‑embodiment description; combining known soft‑magnetic filler (iron powder/permalloy/amorphous) with a moldable resin binder to reduce weight and ease molding is conventional (resin‑bonded magnetic materials), and the motivation (lightweight, moldable, corrosion‑resistant holder cover) is articulated in the specification itself.
• Claim 6 (entire rotatable body is the shield): the third embodiment; combining JP '679 with the resin‑holder art (Ichisawa/Denso) and molding the whole holder from magnetic resin increases saturation and simplifies manufacture — an obvious manufacturing convenience.
• Claims 7–8 (plate part + integral cylindrical plate part; cylinder fitted between magnet outer surface and rotatable body): JP '679's cup (bottom + cylindrical wall over the magnet's outer periphery) and Ogasawara's cylinder+flange disclose the plate‑plus‑cylinder fitted about the magnet outer surface.

8. Anticipated Rebuttals and Where the Patent May Survive

1. No single reference discloses the exact "projection region … entirely covered" + "exposed surface into the container" combination. That is true; the case is a combination case and rises or falls on motivation + reasonable expectation of success.
2. Different problem statements. JP '679 (foreign matter) vs. Yazaki (external magnetic field). A patentee will argue non‑analogous problem → no motivation. Counterpoint: the field of endeavor is identical, and the patent itself frames the shield as limiting flux leakage generally; a POSITA would recognize leakage control serves both problems.
3. Yazaki's shield deliberately does not disturb the magnet field (notched portion facing the magnet/shaft), which arguably teaches away from a shield spanning the magnet footprint. This is the patentee's best argument and should be addressed head‑on: the notch is to avoid perturbing the sensing field, not to avoid covering the inter‑magnet gap; the notch faces the magnet/shaft, not the detection‑element footprint that the claimed shield must cover.
4. Secondary considerations. None are apparent on the face of the record (no evidence of unexpected results, licensing, or copying in the materials reviewed). The grant itself is not evidence of non‑obviousness.

9. Conclusion

• Strongest § 103 challenge to claim 1: JP 2006‑153679 A in view of US 7,331,225 B2 (optionally further in view of Denso's US 2007/0090832 or US 2005/0083045). JP '679 supplies the full sensor architecture and a magnet‑surrounding cup shield; Yazaki supplies an outboard shield plate covering the entire element/stator footprint (the "projection region"), with an outward‑facing surface, plus the stated motivation to stabilize output by shielding the detection region.
• Claims 2–8 are, on the record reviewed, obvious as design choices and geometries taught by the same and additional cited references (Ichisawa; Ogasawara/Nippon Seiki; Denso).
• Confidence: the combination rationale is moderately strong but not a slam dunk, principally because (a) the patent granted over references that were of record, and (b) Yazaki's deliberate field‑conservation notch is a genuine teaching‑away hook. A full validity opinion would require the actual JP '679 figures (to confirm the cup bottom's coverage of the inter‑magnet space) and the prosecution history, which I could not retrieve with the tools available.

Citations: JP 2006‑153679 A (https://patentimages.storage.googleapis.com/f2/5e/52/cb010b49cd26cd/JP2006153679A.pdf); US 7,331,225 B2 (https://patents.google.com/patent/US7331225); US 2005/0083045 A1 (https://patents.google.com/patent/US20050083045); US 2008/0072668 A1 / US 7,458,261 (https://patentimages.storage.googleapis.com/3f/8e/49/a2b28546de0bec/US8028575.pdf); US 2007/0090832 A1 (https://www.freepatentsonline.com/7703322.html); US 2012/0011931 A1 (https://patents.google.com/patent/US20120011931A1/en); US 2015/0000398 A1 / US 9,453,756 B2 (https://patents.google.com/patent/US20150000398, https://patents.google.com/patent/US9453756); patent at issue (https://patents.google.com/patent/US10001400/en).

Two open items I could not resolve: the substance of US 2016/0161321 A1 (Denso sibling) and the JP '679 drawing sheets — both would sharpen the "entire projection region" mapping.